Goodwill In-Process Research and Development and Other Assets - Additional Information (Detail)	12 Months Ended
	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)	Jul. 31, 2014 USD ($)
Goodwill [Line Items]
Goodwill	$ 32,601,000	$ 35,808,000	$ 31,045,000
Accumulated impairment loss, goodwill	0
In-process research and development	15,208,000	16,705,000	14,482,000
Aggregate carrying amount of other investments	80,779,000	12,649,000	7,249,000	$ 4,350,000
Impairment on Other Investments	1,000,000
License Manufacturing Rghts to Technology
Goodwill [Line Items]
Payments to third party	2,800,000
Amortization of intangible assets	$ 200,000	0	$ 0
Other Intangible Assets
Goodwill [Line Items]
Intangible asset, amortized useful life	15 years
Shockwave Medical
Goodwill [Line Items]
Investment in affiliate	$ 25,000,000
Fair value of investment	56,200,000
Shockwave Medical | Other Income
Goodwill [Line Items]
Gain recorded in other income	31,200,000
Medical Device Companies
Goodwill [Line Items]
Aggregate carrying amount of other investments	$ 39,900,000	6,400,000
ECP Entwicklungsgesellschaft mbH
Goodwill [Line Items]
In-process research and development		$ 16,700,000			$ 15,200,000
ECP Entwicklungsgesellschaft mbH | Measurement Input, Discount Rate
Goodwill [Line Items]
Fair value inputs, discount rate	0.21